A cigarette filter is mostly made of cellulose acetate fibers. A cellulose acetate fiber is currently manufactured as follows. Specifically, a cellulose acetate flake is dissolved in a solvent such as acetone, thus preparing a cellulose acetate spinning dope. The spinning dope thus prepared is supplied into a spinning nozzle device and spun using a dry-spinning process at a high temperature, resulting in a cellulose acetate fiber.
In particular, as for a cellulose acetate fiber useful as a fiber for a cigarette filter, in order to facilitate the manufacture of a cigarette filter, total fineness is appropriately set, and a fiber tow having crimps is manufactured. A cigarette filter is fabricated in a manner in which the cellulose acetate fiber tow is opened using a cigarette filter plug winding device, impregnated with a plasticizer, formed into a rod using a filter-winding paper, and cut to a predetermined size.
Commonly, cellulose acetate obtained by subjecting cellulose to acetic acid esterification is known to be a biodegradable material. However, even when a cigarette filter made of cellulose acetate fiber is buried in the soil, its shape is still maintained for 1 to 2 years, and a considerably long period of time is required in order to completely biodegrade the cigarette filter buried in the soil.
The cigarette filter is assembled into a cigarette product, distributed to consumers, provided for smoking, and finally discarded after a cigarette is smoked. Also, the cigarette filter may be directly wasted as the manufacturing residue in the plants for manufacturing a cigarette filter. Such cigarette filter waste is collected as garbage and is then buried. In some cases, the smoked cigarette is not collected as garbage but may be allowed to remain in the natural environment. Cigarette filter waste is not just a visual problem, but it has been found that the toxins in used cigarette filters leach into the environment and potentially represent a biological hazard.
In this situation, there have been proposed various methods of manufacturing a biodegradable cigarette filter. In this regard, in order to increase the rate of decomposition of cellulose acetate as the biodegradable polymer, an additive is added, or cellulose acetate having few substitutions is used to increase biodegradability. Alternatively, as a filter tow material, the use of a polymer composite having high biodegradability comprising PHB (poly-hydroxybutyrate)/PVB(polyvinyl butyral) and starch has been proposed.
However, no satisfactory commercial solution has yet been proposed to produce a filter that can break down quickly enough to overcome the garbage problem and thus be acceptable to consumers. This is because a method capable of simultaneously satisfying the cigarette preference and absorption profile during smoking as a cigarette filter while achieving a biodegradation rate fast enough to solve the environmental problem has not yet been achieved.
Meanwhile, in the case of a lyocell fiber manufactured from natural pulp and amine oxide hydrate, superior tension properties and a superior tactile sense may be exhibited compared to existing regenerated fibers. The amine oxide-based solvent used to prepare the lyocell fiber may be recycled, and may biodegrade even when discarded, and thus the production process does not generate any pollutants, and research on lyocell fibers as an environmentally friendly regenerated fiber has recently become more active.
As disclosed in U.S. Pat. Nos. 4,416,698 and 4,246,221, the method of manufacturing lyocell fiber includes spinning a spinning dope obtained by dissolving cellulose in amine oxide (NMMO) and coagulating it to give filaments, followed by water washing, drying and post-processing. Furthermore, the lyocell fiber is not naturally wound, but may be usefully employed in a manner in which the wet fiber is compressed by the method disclosed in European Patent Application Publication No. 797,696, or in which crimps may be formed through stuffer box-winding processing using a dry vapor by the method disclosed in European Patent Application Publication No. 703,997.
For existing lyocell fibers, blooming properties due to the formation of crimps are not good, and in most conventional techniques, only the physical properties of lyocell fibers, such as strength and the like, are improved. However, the material for a cigarette filter is required to have good crimping properties, and in order to efficiently apply the biodegradable lyocell fiber to the cigarette filter, research and development is ongoing into improving the crimping properties of a lyocell material so as to satisfy the properties required of the material for a cigarette filter by ensuring a large number of crimps.